Direct to-metal and exterior durable non-skid coating

ABSTRACT

A non-skid coating described herein attempts to overcome the deficiencies of the conventional coatings with improved external durability and color retention, a reduced level of VOCs, and direct-to-metal (DTM) adhesion using organo-siloxane chemistry. The non-skid coating has a first component having an amino-functional siloxane resin; a second component having a non-aromatic epoxy resin; a spherical filler for lowering viscosity; a pigment; a coarse aggregate; and a thixotropic agent. The amino-functional siloxane resin can be an amino-functional methyl phenyl polysiloxane, diphenyl polysiloxane or silsesquioxane-based resin. The non-aromatic epoxy resin can be cycloaliphatic or aliphatic. The first component is about 5% to 20% weight of the coating, and the second component is about 80% to 95% weight of the coating.

TECHNICAL FIELD

The present application relates generally to a non-skid coating withimproved exterior durability and direct-to-metal adhesion.

BACKGROUND

The flight decks of U.S. Navy ships are a highly vital component forconducting war-time flight operations, training exercises, and thetransportation of goods to fleet personnel. The surfaces of these decksare coated with a special material that provides a rough and abrasiveprofile so that aircraft, equipment, and sailors do not slide when aship is maneuvering in the open waters. This material, known as a“non-skid” or “non-slip” coating, is located on approximately 4,000,000square feet of flight deck area within the U.S. Navy, with carriersalone possessing a combined surface area of over 2,000,000 square feetof non-skid coating.

The Navy's current non-skid coatings are composed of two components thatare mixed together and applied over an anti-corrosive deck primer usinga phenolic roller. The coating is applied to the deck by a roller tocreate a rough ‘peak and valley’ profile, thereby providing a frictionalsurface to prevent the sliding, moving, or skidding of crew members,aircraft, storage containers, and machinery. To provide this aggressiveprofile, these coatings usually contain aluminum oxide or aluminum metalaggregate for general areas (Type-G) or landing areas (Type-L),respectively. Non-skid coatings have been used by the Navy for decades,yet their long-term performance continues to remain a highly contentiousissue.

Conventional non-skid coatings are typically composed of aromatic epoxyresins (e.g., Bisphenol A, Bisphenol F, or Novolac) and amino-functionalresins (e.g., amidoamine resin), along with fillers, colorizingpigments, and aggregates that are mixed together to create a viscousformula. Due to their inherent chemistry, traditional non-skid coatingsare not durable to the external environment of UV and visible radiation,which is evident by the rapid fading, chalking, and degradation that isroutinely observed within a few months after application. Traditionalnon-skid coatings also contain relatively high levels of volatileorganic compounds (VOCs), usually as solvent(s), which can lead tosolvent entrapment, shrinkage, and cracking as the coating cures. Theseproblems, amongst others, can contribute to performance failures ofnon-skid coatings during routine operations, as exemplified by the lossof abrasive profile, lifting of coating from the deck due to loss ofadhesion, or large areas of corrosion seepage that result from cracks inthe non-skid coating.

Siloxane-based materials, which contain silicone-oxygen bonds, arebecoming increasingly popular within the global coatings market due totheir outstanding external durability, chemical resistance,cleanability, increased thermal stability and low toxicity.Siloxane-based materials are also low in viscosity, thereby leading toreduced VOC requirements when formulated into coatings. Siloxanes can beengineered as linear or branched polysiloxane resins or cyclicstructures (e.g., silsesquioxanes), and each can be functionalized withreactive organic groups.

Hybrid coating technology based on the incorporation of silicone-basedresins (e.g., siloxanes or silanes) with epoxy or amine chemistries canprovide better performance characteristics than traditional epoxy/aminecoatings. For instance, silicone-oxygen bonds are much stronger than thecarbon-carbon and carbon-hydrogen bonds that are typically found intraditional non-skid coatings. This increased bond strength leads to agreater external durability and chemical resistance, thereby extendingthe life-cycle of a coating by preventing the rapid chalking, fadingand/or cracking that occurs due to degradation by ultra-violet (UV) andvisible radiation. On the other hand, the organic portions of a hybridcoating are used to provide substrate binding and flexibility, thusleading to a coating that possesses direct-to-metal (DTM) adhesion anddoes not require a primer.

Silsesquioxanes are low in VOCs, provide good hardness and externaldurability, and can be functionalized with pendant reactive groups.Amino-functional silsesquioxane resins are commercially available andwere used to formulate non-skid coatings as a replacement for thetraditional amine resins (e.g., amidoamines) that often cause yellowing.As for the epoxy component, the traditional aromatic epoxies have beenreplaced with non-aromatic epoxy resins (e.g., zero VOC cycloaliphaticepoxies). These epoxy resins yield similar hardness and performance, yetprovide better external durability due to their lack of aromaticcharacter.

Thus, it is desirable to have a non-skid coating that has greaterexterior durability than conventional coatings.

SUMMARY OF THE INVENTION

The non-skid coating described herein attempts to overcome thedeficiencies of the conventional coatings with improved externaldurability and color retention, a reduced level of VOCs, anddirect-to-metal (DTM) adhesion using organo-siloxane chemistry.

In one embodiment, a non-skid coating comprises a first component havingan amino-functional siloxane resin; a second component having anon-aromatic epoxy resin; a spherical filler for lowering viscosity andreducing VOC content; a pigment; and a coarse aggregate. The coating canalso include a catalyst, a thixotropic agent and a rheology agent. Theamino-functional siloxane resin can be an amino-functional methyl phenylpolysiloxane, diphenyl polysiloxane, or silsesquioxane-based resin. Thenon-aromatic epoxy resin can be cycloaliphatic or aliphatic. The firstcomponent can be about 5% to 20% weight of the coating, and the secondcomponent can be about 80% to 95% weight of the coating.

In another embodiment, a method for producing a non-skid coatingcomprises mixing a first component having an amino-functional siloxaneresin with a second component having a non-aromatic epoxy resin. Thefirst component can also contain an amino-functional additive and acatalyst, while the second component can include a pigment, a sphericalfiller, a thixotropic agent and a rheology agent. The amino-functionalsiloxane resin can be an amino-functional methyl phenyl polysiloxane,diphenyl polysiloxane, or silsesquioxane-based resin. The non-aromaticepoxy resin can be cycloaliphatic or aliphatic. The first component isabout 5% to 20% weight of the coating, and the second component is about80% to 95% weight of the coating. The amino-functional additive can be acycloaliphatic amine or amino-functional alkoxysilane, and can bepresent in 1% to 2% weight of the coating.

Additional features and advantages of an embodiment will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the exemplaryembodiments in the written description and claims hereof.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

DETAILED DESCRIPTION

Reference will now be made in detail to the preferred embodiments of thepresent invention.

In an exemplary embodiment, a coating comprises a first component and asecond component. Before application of the coating, the two componentsare mixed together in specified proportions.

The first component has an amino-functional siloxane resin. Examples ofan amino-functional siloxane resin include an amino-functional methylphenyl polysiloxane/silsesquioxane resin, also known as poly[(2-aminoethyl)aminopropyl]methoxy(dimethyl)siloxane, polymers with[(2-aminoethyl)aminopropyl]phenylsilsesquioxane, OH-term, which iscommercially available as Silres HP 2000 by Wacker Silicones;aminopropylaminoethylpolysiloxane, commercially available as SF1708 fromMomentive; and amino-functional diphenyl polysiloxane resins.

In one exemplary embodiment, the first component is comprised of 139.02grams of amino-functional siloxane resin and 0.75 grams of dibutyl tindilaurate (Aldrich) catalyst (“DBTDL”). In the exemplary embodiment, anon-skid coating (when the first component is combined with the secondcomponent) has about 5% to 20% by weight of the amino-functionalsiloxane resin. In another exemplary embodiment, a non-skid coating hasabout 9% to 14% by weight of the amino-functional siloxane resin.

The second component has a non-aromatic epoxy resin. In the exemplaryembodiment, the non-aromatic epoxy resin is cycloaliphatic, but thenon-aromatic epoxy resin could be aliphatic. An epoxy resin that iscycloaliphatic or aliphatic is more exterior durable than conventionalepoxies that are aromatic. The epoxy resin does not degrade as readilywhen exposed to sunlight (UV and visible radiation) and an oxidativeenvironment. Bisphenol compounds, which are aromatic, are hydrogenatedto remove the aromatics and become cycloaliphatic. As a result, they donot undergo the same degradation process.

In one example, the epoxy resin can be cyclohexanol,4,4-(1-methylethylidene)bis-, polymer with (chloromethyl)oxirane,manufactured by Hexion as Eponex 1510. In other examples, the epoxyresin can be diglycidyl ether of cyclohexane dimethanol, commerciallyavailable as Heloxy Modifier 107 by Hexion; diglycidyl ether ofneopentyl glycol, commercially available as Heloxy Modifier 68 byHexion; diglycidyl ether of 1,4-butanediol, commercially available asHeloxy Modifier 67 by Hexion; trimethylol propane triglycidyl ether,commercially available as Heloxy Modifier 48 by Hexion; polyglycidylether cyclosiloxane monomer, commercially available as CS-697 byDesigner Molecules; and glycidyl ether POSS (polyhedral oligomericsilsesquioxane), commercially available as EPO409 by Hybrid Plastics. Inan exemplary embodiment, a non-skid coating has about 5% to 20% byweight of the non-aromatic epoxy resin. In another exemplary embodiment,a non-skid coating has about 9% to 13% by weight of the non-aromaticepoxy resin.

The second component can also include other materials. For example, thesecond component includes a filler of ceramic microspheres, such asalkali alumino silicate ceramic, which is available as W-610microspheres by 3M. These ceramic microspheres are used instead ofconventional fillers, such as talc, mica, wollastonite or calciumcarbonate, because the microspheres are spherical, rather than plate orrod-like. The spherical, ceramic microspheres reduce the viscosity andsolvent requirements of the second component, as opposed to using theconventional fillers that would require additional solvent, therebyallowing the second component to be more easily assembled and theresulting non-skid coating both rollable and sprayable. The sphericalfiller is about 15% to 20% of the non-skid coating. It should be notedthat reducing the VOC content in coatings is advantageous from anenvironmental standpoint.

The second component can also include an aluminum oxide mixture, whichperforms as a coarse aggregate to provide a coating with a frictionalsurface and hardness. Additionally, the second component can include oneor more thixotropic agents, such as a micronized amide wax (i.e.,CrayVallac PA4BA20), or a rheology agent, such as polyolefin fibers(i.e., polypropylene pulp). The polyolefin fibers also lower the glossof the cured non-skid coating, thereby reducing the reflection ofsunlight off the surface that would otherwise obstruct deck visibilitywhen landing aircraft.

In one exemplary formula, the second component has 123.90 grams of anepoxy resin, available as Eponex 1510 by Hexion; 3.71 grams of titaniumdioxide, available as Ti-Pure R-960 by DuPont; 8.67 grams of copperchromite black spinel pigment, available as V-7709 by Ferro Pigments;182.50 grams of ceramic microspheres, available as W-610 by 3M; 37.50grams of tert-butyl acetate, available from Aldrich; 50 grams ofthixotropic agent, available as CrayVallac PA4BA20 by Cray Valley; 5grams of polypropylene pulp, available as Short Stuff by Mini-Fibers,Inc.; 260 grams of 24 grit brown aluminum oxide, available from KramerIndustries; and 260 grams of 30 grit brown aluminum oxide, availablefrom Industrial Supply, Inc.

An exemplary coating was assembled by mixing two components using a highspeed mixer. The resulting product was a non-skid coating with about91.5% solids (total solvent) or 95% solids (counting VOC exemptsolvents). The coating was applied on various 0.25 inch thick blastedsteels panels using a phenolic roller, then allowed to cure at ambientconditions for approximately seven days before being tested. Table 1,shown below, lists the materials of the first component and the secondcomponent as a percentage of the total non-skid formula.

TABLE 1 Wt. % of First Component Formula Amino-functional siloxane resin  13% Dibutyl tin dilaurate (DBTDL) 0.07% Second Component Epoxy resin11.5% Titanium dioxide 0.34% Copper chromite black spinel 0.81% Ceramicmicrospheres   17% tert-Butyl acetate  3.5% CrayVallac PA4BA20  4.6%Polypropylene pulp 0.46% Aluminum oxide mix 48.5%

The resulting coating showed no cracking or delamination when impactedat twenty-five sites (each 0.75 inches apart to form a grid) with a fourpound weight dropped from 40 inches above the sample, according toMIL-PRF-24667. The coefficient-of-friction (COF) of the coating on an18″×18″×¼″ panel, as measured by a Ball-on-Flat instrument, was 1.71(avg.) at 19.4° C.

The volumetric mix ratios of the first component to the second componentcan be between 3:1 and 5:1. For ease of use in the industry, it may bepreferable to have a ratio of 4:1. In the particular embodiment above,the ratio is 3.4:1 by volume. The following formulas include exemplaryvariations of a 4:1 ratio coating.

Examples of two components for exemplary non-skid coatings are providedbelow. The percentages of each material in the first and secondcomponents are merely exemplary and are not intended to be limited tothose particular percentages or ratios.

In the exemplary formulas below, Silres HP 2000 is used as anamino-functional siloxane resin. In one example,3-aminopropyltriethoxysilane (available from Gelest as SIA0610.0), whichis an amino-functional silane, is used in combination with Silres HP2000 to assist with desirable spray and/or roll viscosity anddirect-to-metal adhesion. In another example,1,3-cyclohexanebis(methylamine) (available from Aldrich), which is acycloaliphatic amine, is used in combination with Silres HP 2000 toassist with desirable spray and/or roll viscosity and coating hardness.

Example 1

Wt. % of First Component Formula DBTDL 0.06% Silres HP 2000 11.43% Second Component Eponex 1510 10.20%  Titanium dioxide (R-960) 0.49%Shepherd Black 30C940 1.55% Shepherd Blue 30C527 0.41% 3M microspheres(W-610) 17.47%  Butyl propionate 3.49% CrayVallac PA4BA20 6.17%Polypropylene pulp 0.61% Aluminum oxide mix 48.10% 

Example 2

Wt. % of First Component Formula DBTDL 0.06% Silres HP 2000 10.07% Gelest SIA0610.0 1.15% Second Component Eponex 1510 11.19%  Titaniumdioxide (R-960) 0.51% Shepherd Black 30C940 1.62% Shepherd Blue 30C5270.42% 3M microspheres (W-610) 18.26%  Butyl propionate 3.22% CrayVallacPA4BA20 5.69% Polypropylene pulp 0.52% Aluminum oxide mix 47.26% 

Example 3

Wt. % of First Component Formula DBTDL 0.06% Silres HP 2000 10.86% 1,3-cyclohexanebis(methylamine) 0.39% Second Component Eponex 1510   12%Titanium dioxide (R-960) 0.26% Shepherd Black 30C940 0.84% Shepherd Blue30C527 0.22% 3M microspheres (W-610) 17.89%  Butyl propionate 2.45%CrayVallac PA4BA20 5.57% Polypropylene pulp 0.44% Aluminum oxide mix  49%

As described herein, organo-siloxane technology has been used to createtwo-component (2K) non-skid coatings with improved external durabilityand color retention, while also providing direct-to-metal adhesion toflight decks in effort to eliminate the need for a deck primer. Thecoatings can also be either spray or roll-applied, unlike thetraditional coatings. Due to the inclusion of silicone-based chemistry,the non-skid coatings contain reduced levels of VOCs and hence a highersolids content (e.g., about 91-95% solids for the hybrid siloxanenon-skid coatings versus about 75-85% solids for traditional epoxynon-skid coatings). The inclusion of siloxanes can also aid withrepelling hydrocarbons (e.g., oil or grease) that would otherwise seepinto the non-skid coating and cause unsafe conditions.

Testing of the 4:1 mix ratio formulas (above) to U.S. Navy non-skidspecifications (MIL-PRF-24667) revealed significant improvements inexterior durability and chemical resistance versus traditional epoxynon-skid coatings. For instance, 400 hours of QUV-B exposure showed nochange in color for the herein siloxane-based non-skid coatings, whereasthe traditional epoxy non-skids were significantly faded and degraded.In chemical resistance tests, such as 24 hour ethanol immersion and 28day detergent immersion, the siloxane-based non-skid coatings remainedin nearly pristine condition, whereas the traditional materials weresoftened and/or discolored.

In alternative embodiments, walnut shells, white aluminum oxide, garnet,aluminum metal, steel shot, or other aggregates can be used instead ofaluminum oxide to provide a rough and hard profile. Low-solar-absorbing(LSA) pigments can be used to reduce the temperature of the decks andcompartments beneath. These include Shepherd Black 30C940, Shepherd Blue300527, Ferro Eclipse Black 10202, Ferro Eclipse Blue 10203, black ironoxide, copper phthalocyanine blue, and red iron oxide, amongst others.Examples of alternative thixotropic and rheology agents can beCrayVallac Extra (100% solids micronized amide wax) and amorphoussilica, respectively, or others known to persons skilled in the art.Numerous solvents, such as tent-butyl acetate, butyl propionate,xylenes, Oxsol 100, PM Acetate or isoamyl acetate, can also be used inthe non-skid/non-slip formulations

The embodiments described above are intended to be exemplary. Oneskilled in the art recognizes that numerous alternative components andembodiments that may be substituted for the particular examplesdescribed herein and still fall within the scope of the invention.

What is claimed is:
 1. A coating prepared by: mixing resins whichconsist of (a) an amino-functional siloxane resin, selected from (i) anamino-functional silsesquioxane-based resin and (ii)3-[2-(aminoethyl)amino]propyl methyl dimethylpolysiloxane, and (b) anon-aromatic epoxy resin; wherein the amino-functional siloxane resinand the non-aromatic epoxy resin are the only resins in the coating; andforming a non-skid coating by applying the mixed components to a surfacewith a roller.
 2. The coating of claim 1, wherein the amino-functionalsiloxane resin is the amino-functional silsesquioxane-based resin. 3.The coating of claim 2, wherein the amino-functionalsilsesquioxane-based resin is poly[(2-aminoethyl)aminopropyl]methoxy(dimethyl)siloxane, polymer with[(2-aminoethyl)aminopropyl]phenylsilsesquioxane, OH-terminal.
 4. Thecoating of claim 1, wherein the non-aromatic epoxy resin iscyclohexanol, 4,4-(1-methylethylidene)bis-, polymer with(chloromethyl)oxirane, diglycidyl ether of cyclohexane dimethanol,diglycidyl ether of neopentyl glycol, diglycidyl ether of1,4-butanediol, trimethylol propane triglycidyl ether, polyglycidylether cyclosiloxane monomer, or glycidyl ether polyhedral oligomericsilsesquioxane.
 5. The coating of claim 1, wherein the coating furthercomprises a spherical filler, a pigment, a thixotropic agent, and anaggregate.
 6. The coating of claim 1; wherein the mixed resins areapplied to the surface with a phenolic roller; and wherein the coatinghas a peak and valley profile.
 7. The coating of claim 1, wherein thecoating comprises about 5% to about 20% amino-functional siloxane resinby weight.
 8. The coating of claim 1, wherein the coating comprisesabout 5% to about 20% non-aromatic epoxy resin by weight.
 9. The coatingof claim 1, further comprising a catalyst.
 10. The coating of claim 1,wherein the non-aromatic epoxy resin is aliphatic or cycloaliphatic. 11.The coating of claim 1, wherein the non-aromatic epoxy resin comprisescyclohexanol, 4,4-(1-methylethylidene)bis-, polymer with(chloromethyl)oxirane.
 12. The coating of claim 1, wherein thenon-aromatic epoxy resin comprises polyglycidyl ether cyclosiloxanemonomer, having the structure

or glycidyl ether polyhedral oligomeric silsesquioxane, having thestructure


13. The coating of claim 1, wherein the coating comprises about 91% toabout 95% solids by weight.
 14. The coating of claim 1, wherein thecoating comprises about 5% to about 20% by weight of the sphericalfiller.